1. Field of the Invention
The present invention relates to optical communication systems, and more particularly to the optical receiver of an optical cross-connect device.
2. Description of the Related Art
In an optical communication system, an optical cross-connect device is typically installed at an intermediate node connecting together the upper node, such as a central base station, and the lower node, such as a subscriber. In addition to the basic functions of transferring and allocating channel signals, the optical cross-connect device plays viable functions of optimizing the data traffic in an optical network and the growth of the network, while improving the abnormal congestion and survivability of the network. In particular, an optical cross-connect device is used in a wavelength division multiplexing (WDM) system and typically includes a demultiplexer, an optical receiver, a cross-connect switch, a controller, an optical transmitter, and a multiplexer.
A conventional receiver in a multi-channel optical communication system typically operates at a particular predetermined bit rate. Hence, the receiver is bit-rate specific. There are diverse transfer formats, known as “protocols,” that are available in optical communication systems. For example, representative transfer formats include SDH/SONET (Synchronous Digital Hierarchy/Synchronous Optical NETwork), FDDI (Fiber Distributed Data Interface), ESCON (Enterprise Systems CONnectivity), optical fiber channel, gigabit Ethernet, and ATM (Asynchronous Transfer Mode). These different protocols provide diverse bit rates of 125 Mb/s, 155 Mb/s, 200 Mb/s, 622 Mb/s, 1,062 Mb/s, 1.25 Gb/s, and 2.5 Gb/s, respectively.
The conventional optical receivers are typically provided with a programmable clock/data reproducing circuit to accommodate different bit rates. The programmable clock/data reproducing circuit reproduces the data and clocks of an input optical signal which is based on a reference clock that is determined on the bit rate of the input optical signal, which is discriminated from a DC level generated based on the respective amplified and delayed from the input optical signal. However, the conventional optical receivers have disadvantages in that there may be an erroneous bit rate determination to data due to the influence of temperature on the circuits for amplifying and delaying the input optical signal, thereby resulting in a degradation in the reliability of the associated optical receiver.